No. 443-] 



< )KGANIC REM A INS. 



797 



deposits. The topography <>|' the neighborhood has to be care- 

 fully studied, and the existing vegetation investigated, especially 

 with regard to composition and relation of the various plant-com- 

 munities. But also ecological conditions have to be observed in 

 this connection, because in some cases they are of considerable 

 help in interpreting the successive evolutional phases of the 

 vegetation. 



